1. Field
The present invention concerns wireless communication, and more specifically, to an apparatus and method of receiving a control channel in a multi-component carrier system.
2. Discussion of the Background
In a wireless communication system, one base station generally provides a service to multiple user equipments. The base station schedules data for multiple user equipments and transmits data alongside control information on the data. In generally, a channel for carrying control information is referred to as a control channel, and a channel that carries data is referred to as a data channel. A user equipment obtains its control information by monitoring a control channel and processes its data using the control information. Monitoring means a user equipment attempting to decode control channel candidates.
A user equipment should receive control information on its data in order to receive the data. However, in a given bandwidth, control channels of a plurality of user equipments are generally multiplexed in one transmission interval. That is, a base station transmits multiple control channels for multiple user equipments in order to provide a service to the user equipments. Each user equipment discovers its control channel among the multiple control channels. If the user equipment fails to correctly detect its control channel from the multiplexed control channels, the data channel cannot be decoded.
A multi-carrier system means a wireless communication system that may support carrier aggregation. The carrier aggregation is a technology that allows for efficient use of a bandwidth broken to pieces and this technology ties several physically non-contiguous bands in the frequency domain, thereby providing such an effect as if a logically large band is used.
A user equipment undergoes a random access procedure so as to access a network. The random access procedure may be divided into a contention-based random access procedure and a non-contention-based random access procedure. The biggest difference between the contention-based random access procedure and the non-contention-based random access procedure lies in whether a random access preamble is designated to be dedicated to a single user equipment. In the non-contention-based random access procedure, a user equipment uses a dedicated random access preamble that is designated only to the user equipment, and thus, no contention (or collision) with other user equipments arises. Here, the “contention” refers to when two or more user equipments attempt to do a random access procedure using the same random access preamble through the same resource. In the contention-based random access procedure, a user equipment uses an arbitrarily selected random access preamble, and thus, a contention is likely to arise.
A user equipment may perform a random access procedure for the purposes of initial access, handover, request for radio resources (scheduling request), timing alignment, etc.